In a vacuum cleaner, high speed rotation of a fan exhausts internal air to establish a pressure difference between inside and outside of the vacuum cleaner, which continuously draws the air around an air suction port into the fan and, at the same time, draws and collects rubbish such as dusts and debris around the air suction port.
Typically, the fan of the vacuum cleaner includes a motor, an impeller and a diffuser. The impeller is connected to the motor, the diffuser surrounds the impeller, the motor drives the impeller to rotate to generate a high pressure airflow, and the diffuser guides the airflow to be quickly exhausted out of the motor. Structure of the diffuser affects velocity distribution and flow rate of the airflow. Therefore, there is a desire for a high efficiency diffuser which can effectively increase the flow rate of the fan and reduce the power consumption.